Negative electrode active material, method for producing the same, secondary battery, and electric device

Abstract

The present application provides a negative electrode active material, a method for manufacturing the same, a secondary battery, and an electric device. The silicon-carbon composite material is included, and the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has an Si2p peak. After undergoing peak splitting processing, the Si2p peak can form the following sub-peaks, including a first sub-peak with a binding energy of 99.7 ± 0.2 eV and a second sub-peak with a binding energy of 98.9 ± 0.2 eV. The peak area ratio of the first sub-peak to the second sub-peak is 1 to 2:1.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode active material, a method for manufacturing the same, a secondary battery, and an electrical device.

Background Art

[0002] In recent years, the application range of secondary batteries has become increasingly wide. Secondary batteries are widely applied in various fields such as power storage systems of hydroelectric, thermal, wind, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. Since secondary batteries have developed greatly, higher requirements are also imposed on energy density, cycle performance, safety performance, etc.

[0003] Silicon-based negative electrode materials are considered to be extremely potential next-generation high-energy density lithium-ion battery negative electrode materials due to advantages such as high theoretical specific capacity, low lithium extraction potential, environmental friendliness, abundant reserves, and low cost.

[0004] In order to further improve battery performance, the prior art requires better negative electrode active materials.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above problems, the present application provides a novel negative electrode active material, a method for manufacturing the same, a secondary battery, and an electrical device, which will be described below respectively.

Means for Solving the Problems

[0006] In a first aspect, the present application provides a negative electrode active material, including a silicon-carbon composite material. The X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p spectrum, the Si2p spectrum has at least one characteristic peak, and the characteristic peak can form the following sub-peaks after peak splitting processing. A first sub-peak with a binding energy of 99.5 to 99.9 eV, and including a second sub-peak with a binding energy of 98.7 to 99.1 eV, the peak area ratio between the first sub-peak and the second sub-peak is 1 to 2:1.

[0007] The negative electrode active material of the above means has a high specific capacity and a long cycle life. It is important that the peak area ratio between the first sub-peak and the second sub-peak is 1 to 2:1. If the peak area ratio between the first sub-peak and the second sub-peak is less than 1, it indicates that the pure silicon content in the negative electrode active material is high and the silicon crystal grains are large, which is disadvantageous for the life. If the peak area ratio between the first sub-peak and the second sub-peak exceeds 2, it indicates that the carbon content in the negative electrode active material is too high, the specific capacity of the active material is low, and the initial effect is poor.

[0008] In some embodiments, the negative electrode active material (1) the binding energy of the first sub-peak corresponds to the binding energy of the Si-C bond, (2) the binding energy of the second sub-peak corresponds to the binding energy of the Si-Si bond, (3) the binding energy of the first sub-peak is 99.6 to 99.8 eV, for example 99.7 eV, (4) the binding energy of the second sub-peak is 98.8 to 99.0 eV, for example 98.9 eV, (5) the peak area ratio between the first sub-peak and the second sub-peak is 1.5 to 2:1, for example 1.6 to 1.8:1, for example 1.7:1, and (6) the content of silicon element in the silicon-carbon composite material is 95 wt% to 99.9 wt% (for example 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% or 99.5 wt%), and the content of carbon element is 0.1 wt% to 5 wt% (for example 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%) includes one or more of the characteristics.

[0009] In some embodiments, the negative electrode active material includes a matrix and the silicon-carbon composite material, and the silicon-carbon composite material is attached to the matrix.

[0010] In some embodiments, the matrix has a porous internal structure, and the silicon-carbon composite material is attached to the outer surface of the matrix and / or the voids of the porous internal structure.

[0011] In some embodiments, the material of the matrix includes one or more of a carbon material, a silicone material, a lithium titanate material, or a combination thereof.

[0012] In some embodiments, the negative electrode active material further includes a carbon coating layer covering the matrix and / or the silicon-carbon composite material.

[0013] In some embodiments, the carbon material includes one or more of a graphite material, a hard carbon material, a soft carbon material, or a combination thereof.

[0014] In some embodiments, the silicon-carbon composite material includes silicon crystallites, and the crystallite size of the silicon crystallites is 20 nm or less.

[0015] In some embodiments, the volume median particle size D V 50 of the negative electrode active material is 1 to 10 μm.

[0016] In some embodiments, the peak intensities of the first sub-peak and the second sub-peak are both less than 2000, for example 1500.

[0017] In a second aspect, the present application provides a method for manufacturing a negative electrode active material, Provide a matrix and a vapor deposition apparatus, place the matrix in a vapor deposition furnace, purge it with an inert gas in advance, and perform step S1 of preheating to a temperature of 200-300 °C, Introduce gas into the vapor deposition apparatus in the first mode, and step S2 includes introducing a silicon source gas and a carbon source gas into the vapor deposition apparatus simultaneously in the first mode, React the silicon source gas and the carbon source gas to deposit a reaction product on the matrix to form a silicon-carbon composite material on the matrix, including step S3, The X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has a Si2p peak, and the Si2p peak can form the following sub-peaks after peak splitting treatment, A first sub-peak with a binding energy of 99.5-99.9 eV, and A second sub-peak with a binding energy of 98.7-99.1 eV, The peak area ratio of the first sub-peak to the second sub-peak is 1-2:1.

[0018] In some embodiments, in step S2, the first mode includes introducing a silicon source gas, a carbon source gas, and an inert gas into the vapor deposition apparatus simultaneously.

[0019] In some embodiments, step S2 (1) The feature that the inert gas is one or more of nitrogen gas and argon gas, and (2) includes one or more features of the feature that the flow rate of the inert gas introduced into the vapor deposition apparatus accounts for 30-85% by volume of the total flow rate of the introduced gas.

[0020] In some embodiments, in step S2, gas is introduced into the vapor deposition apparatus in the first mode, and the air pressure in the apparatus is maintained 200-600 Pa higher than the standard atmospheric pressure.

[0021] In some embodiments, step S3 (1) The feature that step S3 is performed at 400-800 °C, and (2) It has one or more of the characteristics that step S3 continues for 1 to 12 hours.

[0022] In some embodiments, after step S3, It further includes step S4 of depositing a carbon material on the product of step S3.

[0023] In some embodiments, step S4 is After forming a silicon-carbon composite material, an operation of introducing a gas into a vapor deposition apparatus in a second mode, wherein the second mode includes simultaneously introducing a carbon source gas and an inert gas into the vapor deposition apparatus, the ratio of the carbon source gas is 5% to 15%, and the ratio of the inert gas is 85% to 95% operation S4a, and An operation S4b of decomposing a carbon source gas into a carbon material and depositing it on a silicon-carbon composite material.

[0024] In some embodiments, operation S4b is (1) The characteristic that step S4b is performed at 700 to 850 °C, and (2) It has one or more of the characteristics that step S4b continues for 1 to 6 hours.

[0025] In a third aspect, the present application provides a negative electrode active material manufactured by the method described in any one of the above items.

[0026] In a fourth aspect, the present application provides a secondary battery including the negative electrode active material described in any one of the above items.

[0027] In a fifth aspect, the present application provides an electrical device including the secondary battery.

Advantages of the Invention

[0028] One or more embodiments of the present application are (1) The specific capacity of the negative electrode active material is high, (2) The cycle life of the negative electrode active material is long, (3) The cost of the manufacturing method of the negative electrode active material is low, and It has one or more of the beneficial effects that the efficiency of the method for manufacturing the negative electrode active material is high.

Brief Description of the Drawings

[0029]

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Embodiments for Carrying Out the Invention

[0030] Hereinafter, embodiments specifically disclosing the negative electrode active material of the present application, its manufacturing method, the positive electrode sheet, the negative electrode sheet, the secondary battery, the battery module, the battery pack, and the electrical device will be described in detail with appropriate reference to the drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of matters that are already well-known and duplicate descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. Note that the drawings and the following description are provided for those skilled in the art to fully understand the present application and do not limit the subject matter described in the claims.

[0031] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit. A predetermined range is limited by selecting one lower limit and one upper limit, and the boundary of a special range is limited by the selected lower limit and upper limit. The range thus limited may or may not include the boundary values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, when ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also understood to be expected. Note that if the minimum range values 1 and 2, and the maximum range values 3, 4, and 5 are listed, the following ranges, 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 can all be expected. In the present application, unless otherwise explained, the numerical range "a - b" represents an abbreviated expression of any combination of real numbers from a to b, and both a and b are real numbers. For example, the numerical range "0 - 5" represents all real numbers between "0 - 5" listed in this specification, and "0 - 5" is merely an abbreviated expression of these numerical combinations. Also, when a certain parameter indicates an integer ≧2, it corresponds to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and preferred embodiments of the present application can be combined with each other to form new technical solutions.

[0033] Unless otherwise specified, all technical features and preferred technical features of this application can be combined with each other to form new technical solutions.

[0034] Unless otherwise specified, all steps of this application can be performed in order or randomly, and it is preferred to perform them in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, the fact that the method mentioned above may include step (c) means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), or may include steps (c), (a) and (b).

[0035] Unless otherwise specified, the terms "comprise" and "include" mentioned in this application may be either non-limiting or limiting. For example, the above "comprise" and "include" can further comprise or include other components not listed, or can comprise or include only the listed components.

[0036] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the word "A or B" means "A, B, or both A and B". More specifically, any of the following conditions: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) but B is true (or exists), or both A and B are true (or exist) satisfies the condition of "A or B".

[0037] [Secondary battery] A secondary battery, also called a rechargeable battery or a storage battery, refers to a battery in which the active material is activated by charging after the battery is discharged and can continue to be used.

[0038] In a normal case, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery charge and discharge process, active ions (such as lithium ions) are occluded and deintercalated reciprocally between the positive electrode sheet and the negative electrode sheet. The separator is provided between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time, allowing active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly playing a role in conducting active ions.

[0039] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, the negative electrode film layer contains a negative electrode active material, and the negative electrode active material uses the negative electrode active material described in any one of claims of the present application.

[0040] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0041] In some embodiments, a metal foil sheet or a composite current collector can be adopted for the negative electrode current collector. For example, as the metal foil sheet, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0042] In some embodiments, the negative electrode film layer preferably further contains a binder. For example, the binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0043] In some embodiments, the negative electrode film layer preferably further contains a conductive agent. For example, the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0044] In some embodiments, the negative electrode film layer preferably further contains other auxiliary agents such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0045] In some embodiments, the negative electrode sheet can be manufactured as follows. Components for manufacturing the above negative electrode sheet, such as any other components of the negative electrode active material, conductive agent, and binder, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry. The negative electrode slurry is applied to a negative electrode current collector, and after processes such as drying and cold pressing, a negative electrode sheet can be obtained.

[0046] [Negative electrode active material] In some embodiments, the present application provides a negative electrode active material containing a silicon-carbon composite material. The X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has an Si2p spectrum, the Si2p spectrum has at least one characteristic peak, and the characteristic peak can form the following sub-peaks after peak splitting processing. A first sub-peak with a binding energy of 99.5 - 99.9 eV, and A second sub-peak with a binding energy of 98.7 - 99.1 eV. The peak area ratio between the first sub-peak and the second sub-peak is 1 to 2:1.

[0047] The negative electrode active material of the above means has a high specific capacity and a long cycle life. It is important that the peak area ratio between the first sub-peak and the second sub-peak is 1 to 2:1. If the peak area ratio between the first sub-peak and the second sub-peak is less than 1, it indicates that the pure silicon content in the negative electrode active material is high and the silicon crystal grains are large, which is disadvantageous for the life. If the peak area ratio between the first sub-peak and the second sub-peak exceeds 2, it indicates that the carbon content in the negative electrode active material is too high, the specific capacity of the active material is low, and the initial effect is poor.

[0048] In some embodiments, the binding energy of the first sub-peak refers to the binding energy corresponding to the peak value point of the first sub-peak.

[0049] In some embodiments, the binding energy of the second sub-peak refers to the binding energy corresponding to the peak value point of the second sub-peak.

[0050] In some embodiments, the first sub-peak and the second sub-peak have a symmetric peak shape, for example, a peak that conforms to a Gaussian function or a Lorentz function.

[0051] In some embodiments, the binding energy of the first sub-peak is 99.6 to 99.8 eV, for example, 99.7 eV.

[0052] In some embodiments, the binding energy of the second sub-peak is 98.8 to 99.0 eV, for example, 98.9 eV.

[0053] In some embodiments, the peak area ratio between the first sub-peak and the second sub-peak is 1.5 to 2:1, for example, 1.6 to 1.8:1, for example, 1.7:1.

[0054] In some embodiments, the negative electrode active material has one or more of the following characteristics: (1) The binding energy of the first sub-peak corresponds to the binding energy of the Si-C bond. (2) The binding energy of the second sub-peak corresponds to the binding energy of the Si-Si bond, and based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life. (3) The binding energy of the first sub-peak is 99.6 to 99.8 eV, for example, 99.7 eV. (4) The binding energy of the second sub-peak is 98.8 to 99.0 eV, for example, 98.9 eV. (5) The peak area ratio of the first sub-peak to the second sub-peak is 1.5 to 2:1. (6) The content of silicon element in the silicon-carbon composite material is 95 to 99.9 wt% (for example, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt% or 99.5 wt%), and the content of carbon element is 0.1 to 5 wt% (for example, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%).

[0055] Based on this, the negative electrode active material is used in a secondary battery, and the secondary battery exhibits further improved specific capacity, first cycle efficiency, and / or cycle life.

[0056] In some embodiments, the negative electrode active material includes a matrix and the silicon-carbon composite material, and the silicon-carbon composite material is attached to the matrix. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0057] In some embodiments, the matrix has a porous internal structure, and the silicon-carbon composite material is attached to the outer surface of the matrix and / or within the voids of the porous internal structure. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0058] In some embodiments, the material of the matrix includes one or more of a carbon material, a silicone material, a lithium titanate material, or a combination thereof. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0059] In some embodiments, the negative electrode active material further includes a carbon coating layer covering the matrix and / or the silicon-carbon composite material. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0060] In some embodiments, the carbon material includes one or more of a graphite material, a hard carbon material, a soft carbon material, or a combination thereof. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0061] In some embodiments, the silicon-carbon composite material includes silicon crystallites with a crystallite size of 20 nm or less. Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0062] In some embodiments, the volume median particle size D V 50 of the negative electrode active material is 1 to 10 μm (for example, 2 μm, 4 μm, 6 μm, or 8 μm). Based on this, the negative electrode active material has further improved specific capacity, first cycle efficiency, and / or cycle life.

[0063] In some embodiments, the peak intensities of the first sub-peak and the second sub-peak are both less than 2000, for example, less than 1500.

[0064] In some embodiments, the present application provides a method for manufacturing a negative electrode active material, providing a matrix and a vapor deposition apparatus, placing the matrix in a vapor deposition furnace, purging it in advance with an inert gas, and heating it to 200 - 300 °C for preheating in step S1, Step S2 of introducing a gas into the vapor deposition apparatus in the first mode, wherein the first mode includes step S2 of simultaneously introducing a silicon source gas and a carbon source gas into the vapor deposition apparatus, and step S3 of reacting the silicon source gas and the carbon source gas to deposit a reaction product on the matrix to form a silicon-carbon composite material on the matrix, The X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has an Si2p peak, and the Si2p peak can form the following sub-peaks after peak splitting processing, a first sub-peak with a binding energy of 99.5 to 99.9 eV, and including a second sub-peak with a binding energy of 98.7 to 99.1 eV, The peak area ratio of the first sub-peak to the second sub-peak is 1 to 2:1.

[0065] The negative electrode active material obtained based on this means has improved specific capacity, first cycle efficiency and / or cycle life.

[0066] In some embodiments, in step S2, the first mode includes simultaneously introducing a silicon source gas, a carbon source gas and an inert gas into the vapor deposition apparatus. The negative electrode active material obtained based on this means has improved specific capacity, first cycle efficiency and / or cycle life.

[0067] In some embodiments, step S2 (1) the feature that the inert gas is one or more of nitrogen gas and argon gas, and (2) the feature that the flow rate of the inert gas introduced into the vapor deposition apparatus accounts for 30-85% by volume of the total gas flow rate introduced. The negative electrode active material obtained based on this means has improved specific capacity, first cycle efficiency and / or cycle life.

[0068] In some embodiments, in step S2, a gas is introduced into the vapor deposition apparatus in the first mode, and the air pressure in the apparatus is maintained 200 to 600 Pa (for example, 300 Pa, 400 Pa, 500 Pa) higher than the standard atmospheric pressure. The negative electrode active material obtained based on this means has an improved specific capacity, initial effect and / or cycle life.

[0069] In some embodiments, step S3 (1) The feature that step S3 is performed at 400 to 800 °C (for example, 500 °C, 600 °C or 700 °C), and (2) includes one or more of the features that step S3 continues for 1 to 12 hours (for example, 2 hours, 4 hours, 6 hours, 8 hours or 10 hours). The negative electrode active material obtained based on this means has an improved specific capacity, initial effect and / or cycle life.

[0070] In some embodiments, after step S3, step S4 further includes depositing a carbon material on the product of step S3. The negative electrode active material obtained based on this means has an improved specific capacity, initial effect and / or cycle life.

[0071] In some embodiments, step S4 After forming a silicon-carbon composite material, a gas is introduced into the vapor deposition apparatus in the second mode. The second mode simultaneously introduces a carbon source gas and an inert gas into the vapor deposition apparatus. The ratio of the carbon source gas is 5% to 15%, and the ratio of the inert gas is 85% to 95% in operation S4a, and operation S4b of decomposing the carbon source gas into a carbon material and depositing it on the silicon-carbon composite material. The negative electrode active material obtained based on this means has an improved specific capacity, initial effect and / or cycle life.

[0072] In some embodiments, operation S4b (1) The feature that step S4b is performed at 700 to 850 °C (for example, 750 to 800 °C), and (2) It has one or more features that step S4b continues for 1 to 6 hours (for example, 2 hours, 3 hours, 4 hours, or 5 hours). The negative electrode active material obtained based on this means has improved specific capacity, initial effect, and / or cycle life.

[0073] In some embodiments, the present application provides a negative electrode active material manufactured by the method according to any one of the above items.

[0074] In some embodiments, the present application provides a secondary battery including the negative electrode active material according to any one of the above items.

[0075] In some embodiments, the present application provides an electrical device including the above secondary battery.

[0076] [Positive electrode sheet] In some embodiments, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. The positive electrode film layer contains a positive electrode active material.

[0077] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0078] In some embodiments, a metal foil sheet or a composite current collector can be employed for the positive electrode current collector. For example, as the metal foil sheet, an aluminum foil can be used. The composite current collector includes a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the cathode active material can be a cathode active material for batteries well-known in the art. By way of example, the cathode active material can include at least one of olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. The present application is not limited to these materials, and conventional materials that can be used as other battery cathode active materials may also be used. These cathode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include cobalt lithium oxide (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O 2including, but not limited to, at least one of them and its modified compounds. Examples of lithium-containing phosphates with olivine structure include lithium iron phosphate (e.g., LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon, but not limited thereto.

[0080] In some embodiments, the positive electrode film layer preferably further includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0081] In some embodiments, the positive electrode film layer preferably further includes a conductive agent. As an example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be manufactured as follows. Components for manufacturing the above positive electrode sheet, such as any other components of the positive electrode active material, conductive agent, and binder, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is applied to a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode sheet can be obtained.

[0083] [Electrolyte] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. This application is not specifically limited to the type of electrolyte and can be selected as needed. For example, the electrolyte can be in liquid, gelled, or all-solid form.

[0084] In some embodiments, the electrolyte is liquid and contains an electrolyte salt and a solvent.

[0085] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoroborate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoroborate phosphate.

[0086] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0087] In some embodiments, it is preferable that the electrolyte solution further contains an additive. For example, the additive can include a negative electrode film-forming additive and a positive electrode film-forming additive, and can also include additives that can improve certain performances of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature or low-temperature performance of the battery, etc.

[0088] [Separator] In some embodiments, the secondary battery further includes a separator. The present application is not particularly limited to the type of separator, and any known porous separator having good chemical stability and mechanical stability can be selected.

[0089] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator is not particularly limited and may be a single-layer thin film or a multi-layer composite thin film. When the separator is a multi-layer composite thin film, the material of each layer is not particularly limited and may be the same or different.

[0090] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0091] In some embodiments, the secondary battery may include an exterior. The exterior can be used to seal the above electrode assembly and electrolyte.

[0092] In some embodiments, the exterior of the secondary battery may be a hard shell such as a hard plastic shell, an aluminum shell, or a steel shell. The exterior of the secondary battery may also be a soft bag such as a pouch soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0093] The present application is not particularly limited to the shape of the secondary battery, and it may be cylindrical, rectangular, or any other arbitrary shape. For example, FIG. 5 is an example of a rectangular-structured secondary battery 5.

[0094] In some embodiments, referring to FIG. 6, the exterior can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates can surround to form a storage chamber. The housing 51 has an opening communicating with the storage chamber, and the cover plate 53 can be covered over the opening to close the storage chamber. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed within the storage chamber. The electrolyte infiltrates into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual requirements.

[0095] In some embodiments, the secondary battery can be assembled as a battery module, and the number of secondary batteries included in the battery module can be one or more. Regarding the specific number, those skilled in the art can select according to the application and capacity of the battery module.

[0096] FIG. 7 is an example of the battery module 4. Referring to FIG. 7, in the battery module 4, a plurality of secondary batteries 5 are sequentially arranged and installed along the length direction of the battery module 4. Of course, they can be distributed in any other manner. Further, the plurality of secondary batteries 5 can be fixed with fasteners.

[0097] Preferably, the battery module 4 can further include an external case having a storage space, and the plurality of secondary batteries 5 are stored in the storage space.

[0098] In some embodiments, the above battery module can also be assembled as a battery pack, and the number of battery modules included in the battery pack can be one or more. Regarding the specific number, those skilled in the art can select according to the application and capacity of the battery module.

[0099] Figs. 8 and 9 show an example of the battery pack 1. Referring to Figs. 8 and 9, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered by the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0100] Furthermore, the present application further provides an electrical device including at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device and can also be used as the energy storage unit of the electrical device. Examples of the electrical device include, but are not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships, satellites, energy storage systems, etc.

[0101] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to the usage requirements.

[0102] Fig. 10 shows an example of an electrical device. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like. In order to meet the demand for high output and high energy density of the secondary battery of the electrical device, a battery pack or a battery module can be used.

[0103] Hereinafter, embodiments of the present application will be described. The embodiments described below are merely illustrative and are only used for interpreting the present application and should not be understood as limiting the present application. When specific technologies or conditions are not indicated in the embodiments, it is necessary to follow the technologies or conditions described in the literature in the relevant field or the specifications of the products. When the manufacturer of the reagents or equipment used is not indicated, they are conventional products that can be purchased commercially.

[0104] Comparative Example 1 A commercially available silicone material is provided as the negative electrode active material of Comparative Example 1.

[0105] The components of the silicone material are Li 8 wt%, Si 52 wt%, O 35.8 wt%, and C 4.2 wt%.

[0106] Example 1 In S1, a silicone material similar to that of Comparative Example 1 is provided as the matrix. A chemical vapor deposition (CVD) apparatus is provided. 1 kg of the matrix is placed in the reaction chamber of the chemical vapor deposition apparatus. The reaction chamber is purged with nitrogen gas, and the temperature of the reaction chamber is raised to 200°C. In S2, a mixed gas is introduced into the reaction chamber in the first mode. The first mode refers to introducing the mixed gas into the reaction chamber at a volume ratio of monosilane:acetylene:nitrogen gas = 20%:5%:75%, the total flow rate of the gas is 5 L / min, and the pressure in the reaction chamber is controlled to be higher than 200 Pa of atmospheric pressure. In S3, the temperature in the reaction chamber is raised to 600°C, and the reaction product (silicon-carbon composite material) formed by reacting monosilane and acetylene is deposited on the matrix, and the deposition continues for 4 h. In S4, a mixed gas is introduced into the reaction chamber in the second mode. The second mode refers to introducing the mixed gas into the reaction chamber at a volume ratio of acetylene:nitrogen gas = 5%:95%. In S5, the temperature in the reaction chamber is raised to 850°C, acetylene is decomposed to form a carbon material and deposited on the surface of the product of the previous step, and the deposition continues for 2 h. After the product is cooled, it is taken out from the reaction chamber and sieved through a 325-mesh sieve. The negative electrode active material of Example 1 is obtained.

[0107] The negative electrode active material of Example 1 includes a matrix, a first coating layer deposited on the surface of the matrix, and a second coating layer deposited on the surface of the first coating layer. The material of the matrix is a silicone material. The material of the first coating layer is a silicon-carbon composite material. The material of the second coating layer is a carbon material.

[0108] Examples 2 - 3 The difference between Example 2 and Example 1 is that in step S2, the ratio of monosilane:acetylene:nitrogen gas = 20%:7%:73%. The difference between Example 3 and Example 1 is that in step S2, the ratio of adjusted monosilane:acetylene:nitrogen gas = 20%:2%:78%.

[0109] Comparative Examples 2 - 3 The difference between Comparative Example 2 and Example 1 is that in step S2, the ratio of monosilane:acetylene:nitrogen gas = 20%:10%:70%. The difference between Comparative Example 3 and Example 1 is that in step S2, the ratio of monosilane:acetylene:nitrogen gas = 20%:0.5%:79.5%.

[0110] Manufacture of Button-Type Battery Using the negative electrode active materials of Comparative Example 1 and Example 1, assemble them into a button-type lithium-ion battery, specifically as follows: Mix the negative electrode active material, conductive carbon black, and polyacrylic acid as the binder in a mass ratio of 8:1:1. Then, add deionized water as the solvent and stir uniformly with a stirrer to obtain a negative electrode slurry with a solid content of 45 wt%. Uniformly apply the negative electrode slurry to a negative electrode current collector copper foil and dry it at 85°C. After cold pressing, obtain an electrode sheet. Using metallic lithium as the counter electrode, inject and assemble the electrolyte using a Celgard 2400 separator to obtain a button-type battery. The solvent of the electrolyte is a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), and the volume ratio of EC, EMC, and DEC is 20:20:60. The solute of the electrolyte is LiPF 6 and the concentration is 1 mol / L. The electrolyte further contains fluoroethylene carbonate (FEC) as an additive, and the content of FEC in the electrolyte is 5 wt%.

[0111] Analysis and Detection Powder Performance Test 1) XPS Detection The negative electrode active materials of the examples and comparative examples were tested using an X-ray photoelectron spectrometer (Thermo Scientific ESCALAB Xi+), and the Si2p energy spectrum of the materials was obtained. Peak fitting processing was performed on the characteristic peaks of the Si2p energy spectrum using XPSpeak software.

[0112] The Si2p energy spectrum of the negative electrode active material of Comparative Example 1 has one characteristic peak in the range of 100 - 104 eV, and the binding energy of this characteristic peak is 102.3 eV, corresponding to the binding energy of the Si - O - C bond.

[0113] Figure 1 shows the Si2p energy spectrum of the negative electrode active material of Example 1. As shown in Figure 1, the Si2p energy spectrum of the negative electrode active material of Example 1 has the original curve 100. The original curve 100 has one characteristic peak each at 98 - 101 eV and 101 - 105 eV. After performing peak fitting processing on the characteristic peak at 98 - 101 eV, the fitting curve 200 is formed. The fitting curve 200 appears as the superposition of two sub - peaks at the position of 101 - 105 eV. The two sub - peaks are the first sub - peak 201 with a binding energy of 99.7 eV (corresponding to the binding energy of the Si - C bond), and the second sub - peak 202 with a binding energy of 98.9 eV (corresponding to the binding energy of the Si - Si bond), the peak area A of the first sub - peak 201 Si-C and the peak area A of the second sub - peak 202 Si-Si The ratio A Si-C / A Si-Si is 1.7. The peak intensities of the first sub - peak and the second sub - peak are both less than 2000. The A Si-C / A Si-Si test results of each example and comparative example are shown in Table 2.

[0114] 2) XRD test, calculation of crystal grain size, laser diffraction particle size distribution

[0115] In accordance with the test method of JIS K 0131-1996, the XRD spectrum of the above silicon-carbon material was obtained by testing with a Bruker D8 Discover X-ray diffractometer, and the test angle range was 20°-80°. After obtaining the data, fitting was performed with X’Pert Highscore plus software, and the size of the crystal grains of the silicon (111) crystal plane corresponding to 28.5°±0.1° was obtained by calculation using Scherrer's formula.

[0116] The XRD spectra of Example 1 and Comparative Example 1 are shown in Figure 2. From the XRD spectrum of the negative electrode active material of Comparative Example 1, Li 2 SiO 3 and Si diffraction peaks can be observed. The distribution of the diffraction peaks in the XRD spectrum of the negative electrode active material of Example 1 basically coincides with that of the comparative example, but the diffraction peak intensity becomes weaker. This suggests that in Example 1, the silicon-carbon composite material and the carbon material deposited on the matrix hardly have diffraction peaks and basically exhibit an amorphous structure.

[0117] The sizes of the silicon crystal grains calculated based on Scherrer's formula are shown in the following table. The average sizes of the silicon crystal grains in the negative electrode active materials of Comparative Example 1 and Example 1 are in the range of 6nm to 8nm.

[0118] The particle size distribution data of the negative electrode active materials of the examples and comparative examples measured based on the laser diffraction method are shown in the following table. It includes volume distribution particle size data Dv10 (μm), Dv50 (μm), Dv90 (μm), and Dv99 (μm), and quantity particle size distribution data D N 10 (μm). For the particle size test method, refer to the general laser diffraction method in this field, such as GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The particle size distribution data of the negative electrode active materials of Example 1 and Comparative Example 1 are shown in Table 1.

[0119]

Table 1

[0120] 3) Detection of Elemental Composition The detection of elemental components is performed on the negative electrode active material produced in Example 1 according to the following test methods. Carbon content test: In accordance with the test standard of GB / T 20123-2006 / ISO 15350:2000, the carbon content of the material is obtained by testing with an HSC-140 carbon content analyzer.

[0121] Lithium, silicon, and oxygen element content test: The lithium content and silicon content are obtained by testing with an inductively coupled plasma optical emission spectrometer (ICP, iICAP 7400 device) in accordance with the standard EPA 6010D-2014. The oxygen content is calculated from the tested carbon content / lithium content / silicon content, and the oxygen content = 100% - silicon content - carbon content - lithium content.

[0122] The components of the negative electrode active material of Example 1 are Li 6.8 wt%, Si 57 wt%, O 29.7 wt%, and C 6.5 wt%.

[0123] In the negative electrode active material of Example 1, the components of the silicon-carbon composite material constituting the first coating layer are silicon content 97.5% and carbon content 2.5% (calculated according to the silicon content / carbon content before and after vapor deposition). The test results of each example and comparative example are shown in Table 2.

[0124] 4) Initial charge-discharge efficiency of the battery: Procedure for the initial cycle efficiency test: The button-type battery after assembly is left standing for 60 min. Lithium storage capacity: First, discharge at a constant current of 0.05C to 5 mV, then discharge at 50 μA to 5 mV, and leave standing for 10 min. Lithium deintercalation capacity: Charge at 0.1C to 1.5V. The specific capacity-voltage curve of the first lithium storage-lithium deintercalation is shown in Figure 3. The initial cycle efficiency (abbreviated as the initial effect) is calculated by the following formula: Initial effect % = Lithium deintercalation capacity / Lithium storage capacity The test results are shown in Table 2 below.

[0125] As can be seen from Table 2 and FIG. 3 above, compared with Comparative Example 1, the negative electrode active material of Example 1 has significantly increased lithium extraction capacity and lithium intercalation capacity. The initial effect of the negative electrode active material of Example 1 basically corresponds to that of Comparative Example 1. The test results of each example and comparative example are shown in Table 2.

[0126] 5) Detection of battery cycle life: Assemble the negative electrode active materials of the examples and comparative examples as full batteries.

[0127] Method for preparing positive electrode slurry: The positive electrode NCM ternary material, Super P as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder are mixed at a mass ratio of 97:1.5:1.5, and N-methylpyrrolidone (NMP) as the solvent is added. Under the action of a vacuum stirrer, it is uniformly stirred to obtain a positive electrode slurry with a solid content of 77 wt%. The positive electrode slurry is uniformly coated on the aluminum foil of the positive electrode current collector and dried at 85 °C. Next, through cold pressing, trimming, slitting, and cutting, and finally dried under vacuum conditions at 85 °C for 4 h to obtain a preliminary positive electrode sheet.

[0128] Method for preparing negative electrode slurry: The negative electrode active material (90% graphite, 10% silicon), the conductive agent (containing CNTs), sodium carboxymethyl cellulose (CMC) as the thickener, and styrene-butadiene rubber (SBR) as the binder are mixed at a mass ratio of 96.2:1.3:1.0:1.5. After that, deionized water as the solvent is added, and it is uniformly stirred under the action of a vacuum stirrer to obtain a negative electrode slurry with a solid content of 52%. The negative electrode slurry is uniformly coated on the first layer negative electrode film layer and dried at 85 °C. Next, through cold pressing, trimming, slitting, and cutting, and finally dried under vacuum conditions at 120 °C for 12 h to obtain a preliminary negative electrode sheet.

[0129] Method for preparing electrolyte: The organic solvent is a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), where the volume ratio of EC, EMC and DEC is 20:20:60. In an argon gas atmosphere glove box with a water content < 10 ppm, a sufficiently dried lithium salt is dissolved in the above organic solvent, and then 10 wt% of the additive fluoroethylene carbonate (FEC) is added and uniformly mixed to obtain an electrolyte. Here, the concentration of the lithium salt is 1 mol / L.

[0130] The positive electrode slurry is applied to an aluminum foil current collector to obtain a positive electrode sheet, and the negative electrode slurry is applied to a copper foil current collector to obtain a negative electrode sheet. After laminating and winding the positive electrode sheet, separator and negative electrode sheet, it is placed in a battery case, and the electrolyte is injected and sealed to obtain a full cell.

[0131] A charge-discharge cycle test is performed on the full cell, the charge-discharge rate is 0.5C / 1C, the cut-off voltage is 2.5 - 4.25V, and a capacity retention rate - cycle number curve is obtained by testing, as shown in Figure 4. The 200-cycle retention rate test results of each example and comparative example are shown in Table 2 below.

[0132] As can be seen from Table 2 and Figure 4, after 200 cycles of the full cells of Example 1 and Comparative Example 1, the capacity retention rates are 96.6% and 96.8% respectively. Example 1 is almost the same as the capacity retention rate of Comparative Example 1. The materials of Example 1 can significantly improve the specific capacity while maintaining a good capacity retention rate.

[0133] 6) Test of the energy density of the battery cell At 25°C, after the batteries manufactured according to the examples and comparative examples are fully discharged at 1C, they are fully charged at a rate of 1C and then fully discharged at a rate of 1C. The actual discharge energy at this time is recorded. At 25°C, the battery is weighed using an electronic balance. The ratio of the actual discharge energy D / Wh of the battery at 1C to the battery weight m / kg is the actual energy density E of the battery, and E = D / m.

[0134] The energy densities of the full batteries of Example 1 and Comparative Example 1 are 276 Wh / kg and 266 Wh / kg respectively, and the energy density is improved by 3.8%. The test results of the energy densities of each example and comparative example are shown in Table 2 below.

[0135]

Table 2

[0136] After peak fitting of the XPS Si2p spectrum of the negative electrode active material of Examples 1 to 3, the peak area ratio of the first sub-peak to the second sub-peak is 1 to 2:1. The negative electrode active material is used in a secondary battery, and the battery exhibits improved specific capacity, improved initial effect, and excellent cycle life.

[0137] After peak fitting of the XPS Si2p spectrum of the negative electrode active material of Comparative Example 3, the peak area ratio of the first sub-peak to the second sub-peak is less than 1, indicating that the pure silicon content in the negative electrode active material is high and the silicon crystal grains are large, which is disadvantageous for the life. Since the peak area ratio of the first sub-peak to the second sub-peak of Comparative Example 2 is greater than 2, the carbon content in the negative electrode active material is too high, the specific capacity of the active material is low, and the initial effect is poor.

[0138] Note that the present application is not limited to the above embodiments. The above embodiments are illustrative, and any embodiments that have the same technical idea and actually the same configuration and the same effects within the scope of the technical means of the present application are included in the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art and other forms constructed by combining some of the components in the embodiments are also included in the scope of the present application.

Description of Reference Numerals

[0139] 1 Battery Pack 2 Upper Box 3 Lower Box 4 Battery Module 5 Secondary Battery 51 Case 52 Electrode assembly 53 Top cover assembly 11 Positive current collector 112 Surface 12 Conductive base coating 13 Positive electrode film layer

Claims

1. A negative electrode active material containing a silicon-carbon composite material, wherein the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has an Si2p spectrum, the Si2p spectrum has at least one characteristic peak, and the characteristic peak can form the following sub-peaks after peak splitting processing: a first sub-peak with a binding energy of 99.5 to 99.9 eV, and a second sub-peak with a binding energy of 98.7 to 99.1 eV, The negative electrode active material has a peak area ratio of the first sub-peak to the second sub-peak of 1 to 2:

1.

2. (1) The characteristic that the binding energy of the first sub-peak corresponds to the binding energy of the Si-C bond, (2) The characteristic that the binding energy of the second sub-peak corresponds to the binding energy of the Si-Si bond, (3) The characteristic that the binding energy of the first sub-peak is 99.6 to 99.8 eV, (4) The characteristic that the binding energy of the second sub-peak is 98.8 to 99.0 eV, (5) The characteristic that the peak area ratio of the first sub-peak to the second sub-peak is 1.5 to 2:1, and (6) The negative electrode active material according to claim 1, having one or more of the characteristics that the content of silicon element in the silicon-carbon composite material is 95 wt% to 99.9 wt%, and the content of carbon element is 0.1 wt% to 5 wt%.

3. The negative electrode active material according to claim 1 or 2, wherein the negative electrode active material includes a matrix and the silicon-carbon composite material, and the silicon-carbon composite material is attached to the matrix.

4. The matrix has a porous internal structure, and the silicon-carbon composite material is attached to the outer surface of the matrix and / or the voids of the porous internal structure. The negative electrode active material according to claim 3.

5. The material of the matrix includes one or more of a carbon material, a silicone material, a lithium titanate material, or a combination thereof. The negative electrode active material according to claim 3 or 4.

6. The negative electrode active material according to any one of claims 1 to 5, further including a carbon coating layer covering the matrix and / or the silicon-carbon composite material.

7. The carbon material includes one or more of a graphite material, a hard carbon material, a soft carbon material, or a combination thereof. The negative electrode active material according to claim 6.

8. The silicon-carbon composite material is the negative electrode active material according to any one of claims 1 to 7, which contains silicon crystal grains with a crystal grain size of 20 nm or less.

9. The volume median particle diameter D of the negative electrode active material Ｖ 50 is the negative electrode active material according to any one of claims 1 to 8, which is 1 to 10 μm.

10. The negative electrode material according to any one of claims 1 to 9, wherein the peak intensities of the first sub-peak and the second sub-peak are both less than 2000.

11. A method for manufacturing a negative electrode active material, providing a matrix and a vapor deposition apparatus, placing the matrix in a vapor deposition furnace, purging it in advance with an inert gas, and performing a step S1 of preheating by raising the temperature to 200 - 300 °C; introducing a gas into the vapor deposition apparatus in a first mode, the first mode including simultaneously introducing a silicon source gas and a carbon source gas into the vapor deposition apparatus in step S2; reacting the silicon source gas and the carbon source gas to deposit a reaction product on the matrix, and forming a silicon-carbon composite material on the matrix in step S3, the X-ray photoelectron spectroscopy (XPS) of the silicon-carbon composite material has an Si2p spectrum, the Si2p spectrum has at least one characteristic peak, and the characteristic peak can form the following sub-peaks after peak splitting processing, a first sub-peak with a binding energy of 99.5 - 99.9 eV, and a second sub-peak with a binding energy of 98.7 - 99.1 eV, A method for manufacturing a negative electrode active material, wherein the peak area ratio of the first sub-peak to the second sub-peak is 1 - 2:

1.

12. Step S2 is (1) characterized in that the silicon source gas is one or more of monosilane and disilane, and / or (2) characterized in that the carbon source gas is one or more of methane, ethylene, and acetylene, and (3) having one or more of the characteristics that the volume flow rate ratio of the silicon source gas to the carbon source gas is 2 - 10:

1. The method according to claim 11.

13. In step S2, the first mode includes simultaneously introducing a silicon source gas, a carbon source gas, and an inert gas into the vapor deposition apparatus. The method according to claim 11 or 12.

14. Step S2 is (1) characterized in that the inert gas is one or more of nitrogen gas and argon gas, and (2) having one or more of the characteristics that the flow rate of the inert gas introduced into the vapor deposition apparatus accounts for 30 - 85% by volume of the total gas flow rate introduced. The method according to claim 13.

15. The method according to any one of claims 11 to 14, wherein in step S2, a gas is introduced into the vapor deposition apparatus in the first mode, and the atmospheric pressure in the vapor deposition apparatus is maintained to be 200 to 600 Pa higher than the standard atmospheric pressure.

16. Step S3 is (1) a feature that step S3 is performed at 400 to 800 °C, and / or (2) the method according to any one of claims 11 to 14, having one or more of the features that step S3 lasts for 1 to 12 hours.

17. After step S3, The method according to any one of claims 10 to 15, further comprising step S4 of depositing a carbon material on the product of step S3.

18. Step S4 is After forming the silicon-carbon composite material, a gas is introduced into the vapor deposition apparatus in the second mode, and the second mode includes simultaneously introducing a carbon source gas and an inert gas into the vapor deposition apparatus. The ratio of the carbon source gas is 5% to 15%, and the ratio of the inert gas is 85% to 95%. Operation S4a, The method according to claim 17, comprising an operation S4b of decomposing the carbon source gas into a carbon material and depositing it on the silicon-carbon composite material.

19. Operation S4b is (1) a feature that step S4b is performed at 700 to 850 °C, and (2) the method according to claim 18, having one or more of the features that step S4b lasts for 1 - 6 hours.

20. The negative electrode active material manufactured by the method according to any one of claims 11 to 19.

21. A secondary battery including the negative electrode active material according to any one of claims 1 to 10, 20.

22. An electrical device including the secondary battery according to claim 21.

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